Constant voltage source



a: W n- April 17, 1956 Filed Oct. 11, 1954 2 Sheets-Sheet l LOAD INVENTOR.

JOHN F. HYLAND ATTORNEY April 17, 1956 J. F. HYLAND 2,742,601

CONSTANT VOLTAGE SOURCE Filed Oct. 11, 1954 2 Sheets-Sheet 2 LOAD ,42 1,44

INVENTOR. JOHN F. HYLAND 3V7 r I: A?!

ATTORNEY United States Patent CONSTANT VOLTAGE SOURCE John F. Hyland, Minneapolis, Minn., assignor to Minu eapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application October 11, 1954, Serial No. 461,540

6 Claims. (Cl. 321-16) The present invention is concerned with a constant voltage source and more particularly with a constant voltage source utilizing the forward and back conducting characteristics of a semi-conductor diode, such as a silicon diode.

The present invention contemplates the use of rectifying means in a circuit such that an alternating current voltage source is rectified and a partially regulated voltage of a first polarity is applied to a load in combination with an unregulated voltage of an opposite polarity, with the relative magnitudes of the two voltages being controlled to give a substantially constant average direct current voltage across the load. It has been found that the partially regulated and the unregulated voltages, above mentioned, vary with the variations in the alternating current source. However, by adjusting the relative magnitudes of these two voltages the average direct current voltage value across the load can be held substantially constant. This substantially constant voltage is achieved at the expense of ripple. However, this ripple can be filtered out by the use of conventional filter means.

It is therefore an object of the present invention to provide an improved constant voltage source utilizing rectifier means in a circuit whereby a partially regulated voltage of a first polarity is applied to a load and a second unregulated voltage of a second polarity is applied to the load.

It is a further object of the present invention to provide an improved constant voltage source utilizing the current flow characteristics of a semi-conductor diode to partially regulate a voltage of a first polarity to be applied to a load and to apply an unregulated voltage of a second polarity to the load.

These and other objects of the present invention will become apparent upon reference to the specification, claims and drawings of which:

Figure l is a graph showing the voltage-current characteristic of a semi-conductor diode, such as a silicon diode;

Figure 2 is a showing of the present invention;

Figure 3 is a showing of a modification of the present invention; and

Figure 4 is a showing of a second modification of the present invention.

Referring specifically to Figure 1, there is shown a graph of the voltage-current characteristics of a semiconductor diode such as a silicon diode. From this graph it. can be seen that as the forward voltage, which is the voltage to the rightof the current axis, increases the current through the diode increases rather rapidly until the point is reached where there is substantially no voltage variation with the increase of current through the diode. As the voltage is increased in the back direction across the diode, that is to the left of the current axis, the voltage is eventually reached where the diode will conduct in the reverse direction and as the voltage is increased still further the point is reached where there is practically no voltage variation for increased current through the diode.

The present invention utilizes the characteristic as shown in this figure whereby the currentthrough the diode can change substantially without changing the voltage across the diode.

The broken line curves of Figure 1 show the effect of temperature on the characteristics of the diode. The broken line curves are for a higher temperature and from this it can be seen that if the current remains constant and the temperature increases, the voltage across the diode will increase in the case' of a forward voltage or decrease in case 'of a reverse voltage across the diode.

Figure 2 is a showing of the present invention wherein three semi-conductor diodes 10, 11 and 12 are utilized and impedance means comprising the resistors" 13, 1'4 and 15 are provided. A potentiometer 16 having a movable tap 17 is connected in series with the diode 10. A load 60 is shown in the form of a resistor and is shunted by a capacitor 17. The apparatus further includes a capacitor 18 which in combination with the resistors 14 and 15 forms a filter network.

The apparatus of Figure 2 also includes power line conductors 19 and 20 which are connected to a source of alternating current voltage, not shown. The operation of this apparatus is such that on a particular half cycle of the alternating current voltage source, which can be called the positive cycle, current flows through diode 11, re.- sistor 13, resistor 14, resistor 15, and load 60 to power line conductor 20. The diode 12 is connected from the junction of resistors 13 and 14 to power line conductor 20 and it can be seen that diode 12 is connected in a reverse direction as related to the diode 11 in the above traced circuit. Therefore, diode 12 does not conduct in the reverse direction until the voltage between the common connection of resistors 13 and 14 and power line conductor 20 reaches the voltage such as shown in Figure 1 wherein current will flow in a reverse direction. This is called the Zener current or Zener direction as related to semi-conductor diodes such as silicon diodes.

Once diode 12 begins to conduct, the voltage across the diode remains substantially constant while the current through the diode may change. This causes the voltage across load 60, as generated by the above traced current flow, to be regulated to a certain extent.

Considering now the opposite half cycle of the alternating current source, current flows from power line conductor 20 through potentiometer 16, and diode 10 to the power line conductor 19. Current also flows in a similar direction from power line conductor 20 through load 60, conductor 21, conductor 22, potentiometer tap 17, and diode 10 to power line conductor 19. It can be seen that voltage generated across load 60 as a result of the above traced current flow is of a reverse polarity to the voltage due to the first above traced current flow. It can also be seen that this current flow is unregulated and asthe voltage of the alternating current source varies, as does the last above traced current through load 60.

Therefore, two voltages exist across load 60. The first of these is a voltage of a first polarity which is regulated. The second voltage is a voltage of a second or opposite polarity which is unregulated. It will be recognized that as the magnitude of the alternating current source varies, both the regulated and unregulatedvoltage will vary, with the unregulated voltage varying to a larger extent than the regulated voltage. By adjusting potentiometer tap 17 the point can be reached where the change in the voltage of the first polarity is exactly opposed by the change in the voltage of the second polarity. This results in a constant average direct current voltage value across load 60. While" load 60 has been shown as directly connected inparallel with capacitor 17, it is recognized that additional filtering can be provided within the terms of the present invention.

Figure 3 is a showing of a modification of the present invention wherein power line conductors 19 and 20 are provided to be connected to the alternating current source, now shown. Four semi-conductor diodes 31, 32, 33 and 34, are provided. The diodes 31 and 32 are connected to conduct current in opposite directions and are connected in series with a resistor 35 to the power line conductors 19 and 20. Diodes 33 and 34 are connected to conduct current in the same direction and are connected in series with the resistors 36 and 37 to the power line conductors 19 and 20. A potentiometer 38 is connected between diodes 32 and 34 and has a movable tap 39 which connects through a load 40 to power line conductor 20.

Operation of the apparatus of Figure 3 can be explained by again considering a particular half cycle of the alternating current voltage source, which can be called the positive half cycle. When the positive half cycle exists between the power lineconductors 19 and 20 a current flow circuit can be traced from power line conductor 19 through diode 31, resistor 35, the left hand portion of potentiometer 38, and load 40 to power line conductor 20. Diode 32 performs a similar function to the diode 12 of Figure 2 and when the voltage across diode 32, which in this case is a reverse voltage, reaches a given magnitude diode 32 conducts in a reverse direction and serves to regulate the voltage across the load 40.

On the opposite, or negative, half cycle of the alternating current voltage source a current flow circuit can be traced from power line conductor 2% through load 40, the right hand portion of potentiometer 38, resistor 36, and diode 33 to power line conductor 19. It can be seen that this current flow through load 40 is of an opposite direction to the current flow first above traced and is an unregulated current. The tap 39 is utilized to control the relative magnitudes of the regulated and unregulated current.

A second current fiow circuit can be traced from power line conductor 20 through resistor 37, diode 34, resistor 36, and diode 33 to power line conductor 19. It can be seen that this current does not pass through the load 40. However, the function of this current flow circuit, and particularly diode 34 and resistor 37, is to provide temperature compensation. As before explained with connection to Figure l, as the temperature of a diode increases, the current may remain constant but the voltage across the diode will increase in the case of forward current or decrease in the case of reverse current. Therefore, assuming a temperature increase, the current above traced in a reverse direction through diode 32. will decrease. However, the current through diode 34 in the forward direction will increase and the two will balance each other out insofar as the current through the load 40 is concerned. Therefore the average direct current voltage across the load 40 will remain substantially constant. Here again, a filtering means may be provided to filter out the ripple existing across load ill.

Figure 4 is a showing of a further modification of the present invention, with this modification likewise utilizing four semi-conductor diodes 41, 42, 43 and 44. Electrical power is suppiled to the apparatus of Figure 4 by means of power line conductors 19 and 20 which are connected to a source of alternating current voltage, not shown.

The diodes 41 and 42 are connected in series with a resistor 45. It can be seen that in this series connection the'diodes 41 and 42 are connected to conduct current in opposite directions. The diodes 43 and 44 are con nected in series with a resistor 46 and are connected to conduct current in the same direction. A potentiometer 47 having a wiper 48 is connected between the diodes 42 and 44, with the wiper 48 connected through a load 49. to power line conductor 20. A second potentiometer 4 50 having a movable tap 51 is connected between the diodes 42 and 44 and has the tap 51' connected to power line conductor 20.

Operation of Figure 4 will be considered by designating a particular half cycle of the alternating current voltage source as the positive half cycle. When this positive half cycle exists between the power line conductors 19 and 20 a current flow circuit can be traced from power line coductor 19 through diode 41, resistor 45, the left hand portion of potentiometer 47, and load 49 to power line conductor 20. The diode 42 is connected so as not to pass current when the positive half cycle of alternating current voltage exists between the conductors 19 and 20. However, when the voltage across diode 42 in the reverse direction reaches a given magnitude the diode will conduct in the reverse direction such as shown in Figure 1. When this condition is reached, the voltage across diode 42 remains substantially constant while the current fiow therethrough may vary. This reverse current flow through diode 42 can be traced from power line conductor 19 through diode 41, resistor 45, diode 42, and the left hand portion of potentiometer 50 to power line conductor 20. Diode 42 functions to regulate the current flowing though the load 49 and provide a substantially regulated voltage of a first polarity across the load 49.

When the opposite or negative half cycle of voltage exists between the power line conductors 19 and 20 a current flow circuit can be traced from conductor 20 through load 49, the right portion of potentiometer 47, resistor 46, and diode 43 to the power line conductor 19. It can be seen that this current is an unregulated current and fluctuations in the alternating current voltage source cause fluctuations in this above traced current flow.

A second current flow path exists from power line conductor 20 through the right portion of potentiometer 50, diode 44, resistor 46, and diode 43 to power line conductor 19. As in Figure 3, the function of diode 44 is to provide temperature compensation. In this modification the extent of the temperature compensation can be adjusted by movement of potentiometer tap 51.

Movement of potentiometer tap 48 serves the same function as potentiometer tap 17 of Figure 2 and potentiometer tap 39 of Figure 3, namely, to regulate the relative magnitude of the regulated and unregulated voltage existing across the load.

From the above detailed explanation it can be seen that I have provided an improved constant voltage source. While these and other modifications of the present invention will become apparent to those skilled in the art, it is intended that the present invention be limited solely by the scope of the appended claims.

I claim as my invention:

1. A constant voltage source comprising, a source of alternating current voltage, a load, a first rectifying circuit including said source of alternating current voltage and said load and providing a regulated voltage of a first polarity across said load, and a second rectifying circuit including said source of alternating current voltage and said load and providing an unregulated voltage of an opposite polarity across said load.

2. A constant voltage source comprising, a source of unregulated alternating current voltage, a load, rectifying means, an impedance; circuit means connecting said load, said rectifying means and said impedance in a series circuit to said source of alternating current to cause a current of a first sense to pass through said load; voltage regulating means connecting to regulate said current of said first sense and maintain it substantially constant; further rectifying means, and circuit means connecting said load and said further rectifying means to said source of alternating current voltage to cause an unregulated current of an opposite sense to pass through said load.

3. A constant voltage source comprising, a source of unregulated alternating current voltage, a load rectifying means, an impedance; circuit means connecting said load, said rectifying means and said impedance in a series circuit to said source of alternating current to cause a current to pass through said load in a first direction; voltage regulating means connecting to regulate said current of said first direction and maintain it substantially constant; further rectifying means, circuit means connecting said load and said further rectifying means to said source of alternating current voltage to cause an unregulated current to pass through said load in an opposite direction, and means to control the relative magnitudes of said current of said first direction and said current of said opposite direction.

4. A constant voltage source comprising, a source of alternating current voltage, a load, a diode, impedance means, circuit means connecting said diode, load, and impedance means in a series circuit to said voltage source to cause a current to flow through said load in a first direction, a semi-conductor diode shunting said load and connected in a manner so as not to pass current in said first direction until a predetermined voltage is reached across said load, said semi-conductor diode then acting to regulate said voltage, a further diode, a potentiometer having end terminals and a tap, circuit means connecting said potentiometer end terminals and said further diode to said voltage source in a manner to cause current to flow through said circuit means in a direction opposite to said first direction, and further circuit means connecting said potentiometer tap to said load to cause a current of said opposite direction to flow therethrough.

5. A constant voltage source comprising; a source of alternating current voltage; a first diode and a first resistor connected in series, a second diode and a second resistor connected in series, circuit means connecting said first series connected diode and resistor and said second series connected diode and resistor in a series circuit to said source of voltage with said second diode being connected to said first resistor, both of said first and said second diodes being connected to conduct current in a first direction; a third diode and a third resistor connected in series, a fourth diode, circuit means connecting said third series connected diode and resistor in series with said fourth diode to said source of voltage, said third diode being connected in a manner to conduct current in a direction opposite to said first direction and said fourth diode being connected to conduct current in said first direction, a potentiometer having a tap and a pair of end terminals, means connecting one of said end terminals to the connection of said fourth diode to said third resistor and the other of said pair of end terminals to the connection of said second diode to said first resistor; and means including a load connected to said potentiometer tap.

6. A constant voltage source comprising; a source of alternating current voltage having a pair of conductors; a first diode and a first resistor connected in series, a second diode, means connecting said first diode, said first resistor and said second diode in series to one conductor of said source of voltage with said second diode being connected to said first resistor, both said first and said second diodes being connected to conduct current in a first direction; a third diode and a further resistor connected in series, a fourth diode, circuit means connecting said third diode, said further resistor and said fourth diode in series to said one conductor of said source of voltage with said fourth diode being connected to said further resistor, said third diode being connected in a manner to conduct current in a direction opposite to said first direction and said fourth diode being connected to conduct current in said first direction; a first potentiometer having end terminals and a tap, means connecting one of said end terminals to the connection of said second diode and said first resistor and connecting the other of said end terminals to the connecting of said fourth diode and said further resistor; a second potentiometer having end terminals and a tap, circuit means connecting one of said end terminals of said second potentiometer to said second diode and the other of said end terminal to said fourth diode; circuit means connecting the tap of said second potentiometer to the other of said pair of conductors of said voltage source; and circuit means including a load connecting the tap of said first potentiometer to said other of said pair of conductors.

References Cited in the file of this patent UNITED STATES PATENTS 1,967,303 Grant July 24, 1934 2,299,942 Trevor Oct. 27, 1942 2,322,955 Perkins June 29, 1943 2,343,411 Grandstafi et a1 Mar. 7, 1944 2,458,516 Klemperer et al Jan. 11, 1949 2,547,162 Kidd Apr. 3, 1951 

